The rising cost of employee benefits is fueling growth in voluntary benefits—those offered by the company, but paid for entirely by employees, often through payroll deductions.

"Voluntary benefits allow employers to offer a more robust benefits package without necessarily incurring more cost," says Bonnie Brazzell, vice president at Eastbridge Consulting Group. Such benefits range from supplemental life insurance and critical illness and accident policies to pet coverage.

Eastbridge data show that among U.S. companies with 10 or more employees, 66% offered at least one voluntary benefit in 2009, up from 54% in 2006; among companies with more than 2,000 workers, the portion was 87%.